It is known that polyphenolic compounds are relatively widespread and in large amount in the plant kingdom. In the Rosaceae family in particular, the analysis of the polyphenols of apple has led to the identification of at least 37 phenolic compounds, the most abundant of which are chlorogenic acid, procyanidins B1 and B2, epicatechin, phloretin, phloridzin and p-coumaric acid. Some of these compounds have physiological properties such as antioxidant, anti-mutagenic, antiallergic, anticancer and antidiabetic properties, and the like.
There are many other polyphenol-rich products on the market, the most common being extracted from green tea, from grape seeds and from pine bark (U.S. Pat. No 4,698,360, EP A 348 781, EP A 283 349, FR A 1 427 100, FR A 2 092 743, FR A 2 643 073 and FR A 2 372 823). Patent EP A 0 657 169 has already disclosed the extraction of a polyphenolic fraction from unripe fruit (weighting from 3 to 10 grams) of the Rosaceae family. The polyphenolic fraction thus defined is characterized by a high content of derivatives of the hydroxycinnamic acid family (chlorogenic acid, caffeic acid, and p-coumaric acid), and of molecules from the flavanol family (catechin, epicatechin and procyanidin). Analysis by high performance liquid chromatography of an extract obtained from the juice of unripe fruit shows that phloridzin represents less than 7% by weight of the total phenolic compounds, and dihydrochalcones (phloridzin and phloretin) less than 9%.
Among the phenolic compounds, phloretin and its glycosylated derivative, phloridzin, are typical of apple and the other fruit of the Rosaceae family. In particular, phloridzin is found in large amount in the pips, but it is also present in apple juice and skin. Phloridzin has antioxidant activity allowing a cardiovascular protection similar to that of estrogens. Moreover, phloridzin is capable of acting on melanogenesis by activating a cascade of enzymes including tyrosinase, thus allowing increased protection against ultraviolet radiation. Phloridzin also has antidiabetic action by competitive inhibition of the sodium-dependent blood transport of metabolites such as glucose, galactose and the like. Phloridzin is also involved in inhibiting the growth of tumor cells by blocking the activity of protein kinase C.
However, in apple (homogenate or juice), the dihydrochalcones (phloretin and phloridzin) are present in small amount relative to the other polyphenols. Chlorogenic acid and the procyanidins are the major polyphenols in apples, whether these are cider apples or dessert apples, phloridzin and phloretin never representing more than 5% by weight of the total polyphenols of ripe cider apples (analysis of 15 different varieties) (FIGS. 1 and 2).
In the known polyphenolic extracts, the proportions between the various phenolic molecules are conserved relative to the proportions present in the various starting materials, with the exception of the polymeric procyanidins, which are lost or degraded during the extraction.
Polyphenolic extracts rich in hydroxycinnamic acids (caffeic acid, chlorogenic acid and coumaric acid) and in flavanols (catechin, epicatechin and procyanidins), and poor in dihydrochalcones (phloridzin and phloretin) are thus conventionally obtained (FIG. 3).
Apple* in mg/L ofKnown polyphenolicjuice or mg/kg ofextract of applePhenolic compoundhomogenate(in mg/g of powder)Caffeic acidε21.7Catechinε to 150 15.1Chlorogenic acid60 to 1200161.0Procyanidins500 to 5000 69.6(B1 and B2)p-Coumaric acid1 to 1509.3Epicatechinε to 140041.4Phloridzin6 to 10032.7Quercitrinε1.9Phloretin5 to 1009.5Total polyphenols483.4(expressed as phloridzinequivalent)ε = unquantifiable amount*Values compiled from measurements on 15 varieties of cider apples and 3 varieties of dessert apples on 3 harvests.    Karadeniz F & Ekski A. Phenolic compounds in apple juice from different varieties. Report—Scientific Technical Com. Int. Fed. Fruit Juice Producers, (1996), 24, pp. 265-275.    Sanoner P., Guyot S., Marnet N. and Drilleau J. F. Polyphenolic profiles of French cider apples varieties. In ‘Polyphenols, wines and health’, symposium, Bordeaux, (14-16 Apr. 1999).    Sanoner P., Guyot S., Marnet N., Molle D. and Drilleau J. F. Polyphenol profiles of French cider apples varieties. J. Agric. Food Chem. (1999), 47, pp. 4847-4853.
There is only very little, if at all any, caffeic acid naturally present in apples. Caffeic acid is in fact probably a degradation product of chlorogenic acid (Fiedler, 1954, Arzneimittel-Forsch., 4, 41).